Expression of human recombinant plasminogen activators enhances invasion and experimental metastasis of H-ras-transformed NIH 3T3 cells.

Abstract

The gene transfer technique was used to examine the role of plasminogen activator (PA) Tumor cell invasion and metastasis are complex processes affected by a multiplicity of factors whose molecular nature is scarcely defined (13,24,44). Hydrolytic enzymes, including proteinases, were long ago implicated in tumor metastasis to account in part for the ability of tumor cells to detach from the primary lesion, to penetrate through basement membrane surrounding blood vessels, and finally to implant themselves into a remote organ (for reviews, see references 8 and 33). One of the enzymes whose role in metastasis is most controversial is plasminogen activator (PA), a serine proteinase that converts the ubiquitous extracellular zymogen plasminogen into the trypsinlike proteinase plasmin. Plasmin, in turn, dissolves the fibrin network of the blood clot, degrades interstitial glycoproteins such as fibronectin and laminin, and converts procollagenases into collagenases necessary for degradation of basement membrane collagen (8). Such a spectrum of activities renders the plasminogen activation system an ideal candidate to participate in tumor invasion and metastasis, since high levels of PA are closely associated with neoplasia-related phenomena (8, 41). The hypothesis concerning the role of the plasminogen activation system in tumor invasion has recently been supported by studies measuring cellular invasion in vitro in assay systems designed to simplify study of tumor cell invasion and metastasis (30,42). These studies have demonstrated that the passage of tumor cells through a barrier of basement membrane in vitro requires a proteolytic cascade of which the final proteinase collagenase is generated by PA-activated plasmin. That PA may also be involved in tumor invasion under physiological conditions is suggested by the immunocytochemical localization of urokinase-type PA (uPA) in areas of invasive growth of the Lewis lung carcinoma (47). Furthermore, the metastatic spread of the Hep-3 human carcinoma in an avian system was significantly inhibited by antibodies specifically blocking the activity of human uPA without affecting either the local growth of the tumor or the avian uPA activity (37,38). Similarly, inhibition by antibod-* Corresponding author.ies of surface-localized uPA on B16 melanoma cells reduced the capacity of the cells to generate experimental metastasis in mice (20). In contrast to the latter cases, in numerous other studies the role of PA in tumor metastasis was inferred from circumstantial rather than direct evidence (for reviews and detailed lists of references, see references 6, 8, 14, 22, 26, 34, 40, and 43). For example, in sublines derived from transplanted tumors, such as the B16 melanoma and the Lewis lung carcinoma, comparison was made between PA production and metastatic capacity (6,9,14,40,54). Comparison was also made between PA levels of spontaneously arising human tumors of the colon, breast, and prostate and PA produced by their invasive and metastatic derivatives (5,22,26,27,36

Overexpression of urokinase-type plasminogen activator in pancreatic adenocarcinoma is regulated by constitutively activated RelA

“…Axelrod et al (1989) reported H-ras-transformed NIH3T3 cells stably expressing a transfected uPA gene invaded more rapidly than parent cells through a basement membrane and caused a high incidence of pulmonary metastatic lesions after intravenous injection into nude mice. Conversely, inhibition of uPA can reduce the invasion and metastasis in H-ras-transformed NIH3T3 cells (Axelrod et al, 1989;Rao et al, 1993). It has also been reported that inhibition of uPA can reduce the size of prostate cancer tumors or even cause complete remission of cancers in SCID mice (Harvey et al, 1988;Jankun et al, 1997).…”

“…uPA is a prognostic marker in breast cancers (Duy et al, 1990). Axelrod et al (1989) reported H-ras-transformed NIH3T3 cells stably expressing a transfected uPA gene invaded more rapidly than parent cells through a basement membrane and caused a high incidence of pulmonary metastatic lesions after intravenous injection into nude mice. Conversely, inhibition of uPA can reduce the invasion and metastasis in H-ras-transformed NIH3T3 cells (Axelrod et al, 1989;Rao et al, 1993).…”

Overexpression of plasminogen activator inhibitor 2 in human melanoma cells inhibits spontaneous metastasis in scid/scid mice.

“…Overexpression of uPA in poorly metastatic murine melanoma cells (10) or in H-ras-transformed NIH 3T3 fibroblasts (11) enabled these cells to form experimental metastases. Overexpression of enzymatically inactive uPA reduced metastasis of prostate carcinoma cells (12).…”

A ligand-free, soluble urokinase receptor is present in the ascitic fluid from patients with ovarian cancer.

“…ing) the activity of the urokinase-type plasminogen activator (uPA)' ofthe cells (3)(4)(5)(6)(7)(8)(9)(10)(11)(12). uPA is localized at the leading edge ofexperimental and human malignant tumors, ofthe implanting embryo, and of migrating macrophages (13)(14)(15)(16)(17).…”